Our previous investigations have centered on a population-based study in Colombia to determine whether nitrate, N-nitrosoproline (NPro) and/or 3- methyladenine were related to the histopathological status of the gastric mucosa. We have discovered that only individuals diagnosed as having intestinal metaplasia or dysplasia (IM) of the stomach show a high degree of correlation between urinary nitrate and urinary N-nitrosoproline. Individuals with normal or chronic gastritis mucosa showed no correlation. A possible explanation for this observation is the loss of reduced ascorbic acid from gastric juice of IM individuals. We will further test the hypothesis that IM leads to increased synthesis of N-nitroso compounds and that increased dietary ascorbic acid inhibits nitrosation. In addition to direct measures of N-nitroso compounds, 15NO3 will be used to establish gastric losses and incorporation of 15N into NPro in individuals with IM compared to normal gastric mucosa. This proposal is a further test of the hypothesis that endogenously formed N-nitroso compounds are risk factors for gastric cancer.